For many applications it is desirable to modify fats using trans-esterification for various technical requirements, in particular when the production of motor fuels from biological sources is required.
There are known processes of this type for the trans-esterification of various vegetable oils and fats which form a multistage process, which is non-continuous and carried out in stages, finally resulting in glycerin, water and the desired methyl esters of the fatty acids, which initially formed an ester with the glycerin. It is also possible to use a different short chain alcohol, for example ethanol, propanol, butanol and in some cases even pentanol, to form the corresponding esters instead of the methyl alcohol. However, methyl alcohol is usually used for economic reasons and due to the simplicity of the reaction. As the length of the chain increases, the acid catalysis becomes more efficient and as such becomes a serious alternative. Impurities in the raw material should be removed to the extent that they do not cause any problems in the process. Prior cleaning of the oil reduces the disadvantages caused by impurities: side reactions, an increased use of chemicals, a slower conversion, etc.
On the other hand, problems are caused by the slow process, which involves treatment of the raw oils with methyl alcohol, usually catalyzed in a large volume mixing vessel for periods usually measured in hours. This reaction stage is followed by a separation stage which in turn takes place in a large settling vessel where any glycerin present collects at the bottom and the intermediate product, which has been up to 90% or more converted, floats although sometimes only after several hours of separation.
The floating intermediate product is once again introduced into a reaction vessel and again transformed using methyl alcohol and alkali, whereby a transformation of about 99% or more of the raw material is reached after several hours.
This product also has to be decanted which also takes place in a large separation vessel where the product floats and is finally drawn off. It is this product which finally undergoes final product purification.
The acid esterification of the fatty acids takes place analogous to the trans-esterification described above, except that the reaction takes place more slowly and water is produced as a side product instead of glycerin. The reaction is normally catalyzed with acid. The invention relates equally to the acid esterification and the trans-esterification of fatty acids and oils or of fats in mixtures with each other as well as with other components.
In summary, it is clear that the current most commercially used processes work in the manner described above. In principle, all these processes are based on early developments which were developed for the production of fatty acid methylesters as raw materials for the chemical industry (U.S. Pat. Nos. 2,360,844, 2,383,632).
The invention is characterized by the fact that (a) technically clean short chain alcohol(s) is/are dispersed into the oil(s) or fat(s) present as a liquid raw material and perhaps contaminated with free fatty acids in the presence of a basic or acidic catalyst. In other words, the invention concerns processes for the basic or acid catalyzed acid esterification and/or trans-esterification of fatty acids and/or oils and/or fats, that is the esters of glycerin with fatty acids, through introduction of short chain alcohols. In particular, methyl alcohol, is introduced into the liquid raw material. Further the process uses commercially pure short chain alcohol(s) dispersed into oil(s) or fat(s) present as a liquid raw material and perhaps contaminated with free fatty acids in the presence of a basic or acid catalyst. In one example, methyl alcohol is used as the alcohol and is completely dispersed in the reaction mixture. The dispersion can have a globule size (diameter) of about 1 μm, and preferably about 5 μm. Indeed, the dispersion can have a globule size of less than 50 μm, and preferably under 15 μm. In another aspect, the dispersion is produced using a dispersion machine, in particular a multi-stage high power dispersion machine.
In the case of the invented process, the dispersion is produced with normal dispersion equipment. This equipment is designed to produce a temporarily stable dispersion. It was often assumed that the mixture created in the dispersion equipment separates only very slowly and because of that the separation times for the glycerin phase were very long. It could be demonstrated, however, that a very rapid phase separation occurs through selection of the correct dispersion equipment.